Effect of continuous and intermittent electric current on lignin wastewater treatment and microbial community structure in electro-microbial system.

In this study, complex structured soluble lignin wastewater was treated by electro-microbial system (EMS) using different direct current (DC) application modes (CR (continuous ON), IR12h (12 h-ON/12 h-OFF) and IR2h (2 h-ON/2 h-OFF)), and physiological characteristics and microbial communities were investigated. Results showed that CR, IR12h and IR2h had higher lignin removals, which were almost two times that of the control reactor (R0', no current), and IR2h performed best and stably. Furthermore, IR2h exhibited the lowest ohmic resistance (Rs) of electrode biofilms, which could be explained by its higher abundance of electroactive bacteria. In the activated sludge of EMS, the concentration of dehydrogenase activity (DHA) and electronic transport system (ETS) in IR2h were the highest (1.48 and 1.28 times of R0'), which contributed to its high content of adenosine triphosphate (ATP). The viability of activated sludge was not affected by different DC application modes. Phospholipid fatty acids (PLFA) analysis indicated that IR2h had the maximum content of C15:1 anteiso A, C16:0 and C18:0; CR increased the content of C15:0 anteiso and decreased the content of saturated fatty acids. Genus-level results revealed that lignin-degrading bacteria, Pseudoxanthomonas and Mycobacterium, could be enriched in IR2h and CR, respectively.

Rhodanobacter hydrolyticus sp. nov., a novel DNA- and tyrosine-hydrolysing gammaproteobacterium isolated from forest soil.

A bacterial isolate, designated G-5-5T, was isolated from forest soil at Kyonggi University. Strain G-5-5T was acid-tolerant and alkali-tolerant. Cells were strictly aerobic, Gram-stain-negative, catalase- and oxidase-positive, non-motile, non-spore-forming, rod-shaped, and yellow-coloured. Strain G-5-5T hydrolysed DNA and tyrosine; assimilated d-glucose, maltose, N-acetyl-glucosamine and l-fucose; and tolerated only 0.5 % NaCl (w/v). Phylogenetic analysis based on its 16S rRNA gene sequence revealed that strain G-5-5T formed a lineage within the family Rhodanobacteraceae and that it grouped with but was distinct from various members of the genus Rhodanobacter. The closest member was Rhodanobacter umsongensis GR24-2T (97.8 % sequence similarity). The sole respiratory quinone was Q-8. The major polar lipids of strain G-5-5T were phosphatidylethanolamine, phosphatidyl-N-methylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The major cellular fatty acids were summed feature 9 (iso-C17 : 1ω9c and/or C16 : 0 10-methyl), iso-C15 : 0, iso-C17 : 0, iso-C16 : 0 and anteiso-C15 : 0. The DNA G+C content of strain G-5-5T was 64.1 mol%. DNA-DNA hybridization relatedness between strain G-5-5T and other close members of the genus Rhodanobacter ranged from 19 % to 45 %. On the basis of the polyphasic characterization and phylogenetic analyses, strain G-5-5T represents a novel species of the genus Rhodanobacter, for which the name Rhodanobacter hydrolyticus sp. nov. is proposed. The type strain is G-5-5T (=KEMB 9005-533T=KACC 19113T=NBRC 112685T).

Chujaibacter soli gen. nov., sp. nov., isolated from soil.

A Gram-staining-negative, aerobic, non-flagellated, rod-shaped bacterial strain, KIS55-21(T), was isolated from a soil sample from Chuja Island, Jeju Province, Republic of Korea. Strain KIS55-21(T) grew optimally at pH 7.0, at 28-30°C and in the presence of 0% (w/v) NaCl. Neighbor-joining and maximum-likelihood trees based on the 16S rRNA gene sequences revealed that strain KIS55-21(T) fell within the family Xanthomonadaceae and was closely related to Metallibacterium scheffleri DKE(T). Strain KIS55-21(T) exhibited the highest 16S rRNA gene sequence similarity (92.6%) to that of M. scheffleri DKE(T), with similarities of less than 92.0% to those of the genera Dokdonella, Rhodanobacter, Aquimonas, and Frateuria. Strain KIS55-21(T) contained ubiquinone-8 (Q-8) as the predominant ubiquinone, iso-C17:0, summed feature 9 (iso-C17:1 ω9c and/or C16:0 10-methyl), anteiso-C17:0 and C16:0 as the major fatty acids, and phosphatidylethanolamine, aminophospholipid, phosphatidylglycerol, diphosphatidylglycerol, and phosphatidylmonomethylethanolamine as the main polar lipids. The DNA G+C content of strain KIS55-21(T) was 65.9 mol%. Differential phenotypic and chemotaxonomic properties and phylogenetic data of strain KIS55-21(T) demonstrated that this strain is distinguishable from closely related genera within the family Xanthomonadaceae. On the basis of the data presented, strain KIS55-21(T) is considered to represent a novel genus and species, for which the name Chujaibacter soli gen. nov., sp. nov. is proposed. The type strain is KIS55-21(T) (=KACC 16971(T) =DSM 28578(T)).

Bacteria of the genus Dyella can chronically colonise the airways of patients with cystic fibrosis and elicit a pronounced antibody response.

A patient with cystic fibrosis became chronically colonised with an unusual non-fermenting Gram-negative rod that could be cultured on Burkholderia cepacia selective agar. Phenotypic characterisation by VITEK-2 suggested identification as Elizabethkingia meningoseptica, however 16S rRNA gene sequencing revealed it belonged to a putative novel species of genus Dyella. Thirty months after the initial detection, the patient produced a high level of precipitating antibodies against the bacterium.

Aerobic uranium immobilization by Rhodanobacter A2-61 through formation of intracellular uranium-phosphate complexes.

Severe environmental problems arise from old uranium mines, which continue to discharge uranium (U) via acid mine drainage water, resulting in soil, subsoil and groundwater contamination. Bioremediation of U contaminated environments has been attempted, but most of the conceptual models propose U removal by cell suspensions of anaerobic bacteria. In this study, strain Rhodanobacter A2-61, isolated from Urgeiriça Mine, Portugal, was shown to resist up to 2 mM of U(vi). The conditions used (low nutrient content and pH 5) potentiated the interaction of the toxic uranyl ion with the tested strain. The strain was able to remove approximately 120 µM of U(vi) when grown aerobically in the presence of 500 µM U. Under these conditions, this strain was also able to lower the phosphate concentration in the medium and increased its capacity to take up inorganic phosphate, accumulating up to 0.52 µmol phosphate per optical density unit of the medium at 600 nm, after 24 hours, corresponding approximately to the late log phase of the bacterial culture. Microscopically dense intracellular structures with nanometer size were visible. The extent of U inside the cells was quantified by LS counting. EDS analysis of heated cells showed the presence of complexes composed of phosphate and uranium, suggesting the simultaneous precipitation of U and phosphate within the cells. XRD analysis of the cells containing the U-phosphate complexes suggested the presence of a meta-autunite-like mineral structure. SEM identified, in pyrolyzed cells, crystalline nanoparticles with shape in the tetragonal system characteristic of the meta-autunite-like mineral structures. U removal has been reported previously but mainly by cell suspensions and through release of phosphate. The innovative Rhodanobacter A2-61 can actively grow aerobically, in the presence of U, and can efficiently remove U(vi) from the environment, accumulating it in a structural form consistent with that of the mineral meta-autunite inside the cell, corresponding to effective metal immobilization. This work supports previous findings that U bioremediation could be achieved via the biomineralization of U(vi) in phosphate minerals.

Phenanthrene degradation by Pseudoxanthomonas sp. DMVP2 isolated from hydrocarbon contaminated sediment of Amlakhadi canal, Gujarat, India.

Amlakhadi canal, flowing through Ankleshwar (Gujarat, India) has been impinged with various xenobiotic compounds, released in industrial discharges, over last many decades. Twenty five bacterial strains capable of phenanthrene degradation were isolated from sediments of Amlakhadi canal. The best strain amongst them was identified as Pseudoxanthomonas sp. DMVP2 based on 16S rRNA gene sequence analysis, and selected for further studies. Experiments were carried out for optimization of abiotic parameters for efficient phenanthrene degradation. Strain DMVP2 was able to degrade 300 ppm of phenanthrene completely in minimal medium containing peptone (0.1%, w/v) as nitrogen source with initial pH 8.0 at 37°C under shaking condition (150 rpm) within 120 h. Strain DMVP2 was able to consume 1,600 mg/l of phenanthrene even at high initial concentration (4,000 mg/l) of phenanthrene. Identification of phthalic acid as major metabolite on GC-MS analysis and detection of protocatechuate dioxygenase activity revealed that phenanthrene was metabolized by phthalic acid-protocatechuate acid pathway. Strain DMVP2 was also able to utilize other xenobiotic compounds as sole carbon source and degrade phenanthrene in presence of other petroleum hydrocarbons. Consequently, Pseudoxanthomonas sp. DMVP2 has potential applications in bioremediation strategies.

A catabolic pathway for the degradation of chrysene by Pseudoxanthomonas sp. PNK-04.

The chrysene-degrading bacterium Pseudoxanthomonas sp. PNK-04 was isolated from a coal sample. Three novel metabolites, hydroxyphenanthroic acid, 1-hydroxy-2-naphthoic acid and salicylic acid, were identified by TLC, HPLC and MS. Key enzyme activities, namely 1-hydroxy-2-naphthoate hydroxylase, 1,2-dihydroxynaphthalene dioxygenase, salicylaldehyde dehydrogenase and catechol-1,2-dioxygenase, were noted in the cell-free extract. These results suggest that chrysene is catabolized via hydroxyphenanthroic acid, 1-hydroxy-2-naphthoic acid, salicylic acid and catechol. The terminal aromatic metabolite, catechol, is then catabolized by catechol-1,2-dioxygenase to cis,cis-muconic acid, ultimately forming TCA cycle intermediates. Based on these studies, the proposed catabolic pathway for chrysene degradation by strain PNK-04 is chrysene → hydroxyphenanthroic acid → 1-hydroxy-2-naphthoic acid → 1,2-dihydroxynaphthalene → salicylic acid → catechol →cis,cis-muconic acid.

Determinative factors of competitive advantage between aerobic bacteria for niches at the air-liquid interface.

We focused on bacterial interspecies relationships at the air-liquid interface where the formation of pellicles by aerobes was observed. Although an obligate aerobe (Brevibacillus sp. M1-5) was initially dominant in the pellicle population, a facultative aerobe (Pseudoxanthomonas sp. M1-3) emerged and the viability of M1-5 rapidly decreased due to severe competition for oxygen. Supplementation of the medium with carbohydrates allowed the two species to coexist at the air-liquid interface. These results indicate that the population dynamics within pellicles are primarily governed by oxygen utilization which was affected by a combination of carbon sources.

Stretches of alternating pyrimidine/purines and purines are respectively linked with pathogenicity and growth temperature in prokaryotes.

BACKGROUND: The genomic fractions of purine (RR) and alternating pyrimidine/purine (YR) stretches of 10 base pairs or more, have been linked to genomic AT content, the formation of different DNA helices, strand-biased gene distribution, DNA structure, and more. Although some of these factors are a consequence of the chemical properties of purines and pyrimidines, a thorough statistical examination of the distributions of YR/RR stretches in sequenced prokaryotic chromosomes has to the best of our knowledge, not been undertaken. The aim of this study is to expand upon previous research by using regression analysis to investigate how AT content, habitat, growth temperature, pathogenicity, phyla, oxygen requirement and halotolerance correlated with the distribution of RR and YR stretches in prokaryotes. RESULTS: Our results indicate that RR and YR-stretches are differently distributed in prokaryotic phyla. RR stretches are overrepresented in all phyla except for the Actinobacteria and beta-Proteobacteria. In contrast, YR tracts are underrepresented in all phyla except for the beta-Proteobacterial group. YR-stretches are associated with phylum, pathogenicity and habitat, whilst RR-tracts are associated with phylum, AT content, oxygen requirement, growth temperature and halotolerance. All associations described were statistically significant with p < 0.001. CONCLUSION: Analysis of chromosomal distributions of RR/YR sequences in prokaryotes reveals a set of associations with environmental factors not observed with mono- and oligonucleotide frequencies. This implies that important information can be found in the distribution of RR/YR stretches that is more difficult to obtain from genomic mono- and oligonucleotide frequencies. The association between pathogenicity and fractions of YR stretches is assumed to be linked to recombination and horizontal transfer.

Network relationships of bacteria in a stable mixed culture.

We investigated the network relationships of bacteria in a structurally stable mixed culture degrading cellulose. The mixed culture consists of four bacterial strains (a cellulose-degrading anaerobe [strain S], a saccharide-utilizing anaerobe [strain F], a peptide- and acetate-utilizing aerobe [strain 3] and a peptide-, glucose-, and ethanol-utilizing aerobe [strain 5]). Interspecies interactions were examined by analyzing the effects of culture filtrates on the growth of the other strains and by comprehensively analyzing population dynamics in the mixed-culture systems with all possible combinations of the four bacterial strains. The persistence of strain S depends on the effects of strain 5. However, strain 5 is a disadvantaged strain because strain 3 has bacteriocidal activity on strain 5. The extinction of strain 5 is indirectly prevented by strain F that suppresses the growth of strain 3. Although strain F directly has suppressive effects on the growth of strain S, strain F is essential for the persistence of strain S, considering the indirect effects (maintaining strain 5, which is essential for the survival of strain S, by inhibiting strain 3). These indirect relationships form a bacterial network in which all the relationships including suppressive effects were well balanced to maintain the structural stability. In addition to direct metabolite interactions, such kind of indirect relationships could have a great impact on microbial community structure in the natural environment.

The role of clp-regulated factors in antagonism against Magnaporthe poae and biological control of summer patch disease of Kentucky bluegrass by Lysobacter enzymogenes C3.

A global regulator was previously identified in Lysobacter enzymogenes C3, which when mutated, resulted in strains that were greatly reduced in the expression of traits associated with fungal antagonism and devoid of biocontrol activity towards bipolaris leaf-spot of tall fescue and pythium damping-off of sugarbeet. A clp gene homologue belonging to the crp gene family was found to globally regulate enzyme production, antimicrobial activity, and biological control activity expressed by Lysobacter enzymogenes C3 (Kobayashi et al. 2005). Here, we report on the expansion of the biocontrol range of L. enzymogenes C3 to summer patch disease caused by Magnaporthe poae. The clp- mutant strain 5E4 was reduced in its ability to suppress summer patch disease compared with the wild-type strain C3 and was completely devoid of antifungal activity towards M. poae. Furthermore, cell suspensions of 5E4 were incapable of colonizing M. poae mycelium in a manner that was distinct for C3. Strain C3 demonstrated biosurfactant activity in cell suspensions and culture filtrates that was associated with absorption into the mycelium during the colonization process, whereas 5E4 did not. These results describe a novel interaction between bacteria and fungi that intimates a pathogenic relationship.

[Effect of the proteolytic enzymes of Bacillus licheniformis and the lysoamidase of Lysobacter sp. XL1 on Proteus vulgaris and Proteus mirabilis].

Preparations of culture liquid of three Bacullus licheniformis strains (S, 103, and 60.4) and the enzymatic preparation lysoamidase from culture liquid of Lysobacter sp. strain XL1 actively lysed preliminarily autoclaved cells of gram-negative bacteria Proteus vulgaris and P. mirabilis. Living Proteus cells treated with these enzymatic preparations were lysed during their subsequent autoclaving. Inoculation of enzyme-treated Proteus cells, taken either separately or in combination with one another and polymyxin B, into a rich medium led to cell repair and restoration of viability of culture.

Suppression of damping-off disease in host plants by the rhizoplane bacterium Lysobacter sp. strain SB-K88 is linked to plant colonization and antibiosis against soilborne Peronosporomycetes.

We previously demonstrated that xanthobaccin A from the rhizoplane bacterium Lysobacter sp. strain SB-K88 suppresses damping-off disease caused by Pythium sp. in sugar beet. In this study we focused on modes of Lysobacter sp. strain SB-K88 root colonization and antibiosis of the bacterium against Aphanomyces cochlioides, a pathogen of damping-off disease. Scanning electron microscopic analysis of 2-week-old sugar beet seedlings from seeds previously inoculated with SB-K88 revealed dense colonization on the root surfaces and a characteristic perpendicular pattern of Lysobacter colonization possibly generated via development of polar, brush-like fimbriae. In colonized regions a semitransparent film apparently enveloping the root and microcolonies were observed on the root surface. This Lysobacter strain also efficiently colonized the roots of several plants, including spinach, tomato, Arabidopsis thaliana, and Amaranthus gangeticus. Plants grown from both sugar beet and spinach seeds that were previously treated with Lysobacter sp. strain SB-K88 displayed significant resistance to the damping-off disease triggered by A. cochlioides. Interestingly, zoospores of A. cochlioides became immotile within 1 min after exposure to a SB-K88 cell suspension, a cell-free supernatant of SB-K88, or pure xanthobaccin A (MIC, 0.01 microg/ml). In all cases, lysis followed within 30 min in the presence of the inhibiting factor(s). Our data indicate that Lysobacter sp. strain SB-K88 has a direct inhibitory effect on A. cochlioides, suppressing damping-off disease. Furthermore, this inhibitory effect of Lysobacter sp. strain SB-K88 is likely due to a combination of antibiosis and characteristic biofilm formation at the rhizoplane of the host plant.

Rhizosphere-induced selenium precipitation for possible applications in phytoremediation of se polluted effluents.

Two bacterial isolates were obtained in axenic culture from the rhizosphere soil of Astragalus bisulcatus, a legume able to hyperaccumulate selenium. Both strains resulted of particular interest for their high resistance to the toxic oxyanion SeO3(2-) (selenite, Se(IV)). On the basis of molecular and biochemical analyses, these two isolates were attributed to the species Bacillus mycoides and Stenotrophomonas maltophilia, respectively. Their capability in axenic culture to precipitate the soluble, bioavailable and highly toxic selenium form selenite to insoluble and relatively non-toxic Se(0) (elemental selenium) was evaluated in defined medium added with 0.2 or 0.5 mM Se(IV). Both strains showed to completely reduce 0.2 mM selenite in 120 h, while 0.5 mM Se(IV) was reduced up to 67% of the initial concentration by B. mycoides and to about 50% by S. maltophilia in 48 h. Together in a dual consortium, B. mycoides and S. maltophilia increased the kinetics of selenite reduction, thus improving the efficiency of the process. A model system for selenium rhizofiltration based on plant-rhizobacteria interactions has been proposed.

Influence of the temperature and the growth phase on the hopanoids and fatty acids content of Frateuria aurantia (DSMZ 6220).

The main lipids isolated from Frateuria aurantia (DSMZ 6220) are iso-branched fatty acids and triterpenoids of the hopane family like bacteriohopanetetrol and derived hopanoids, beside trace amounts of diploptene and rearranged compounds like fern-7-ene. The impact of the growth temperature and the growth phase in which cells were harvested on this lipid fingerprint was investigated. As expected, an increase of saturated compounds with temperature is the essential modification in the fatty acid composition. The fatty acid composition also varies significantly during the growth. Global lipid fingerprints, including at least PLFA and triterpenoids are suggested to be a tool for measuring the stress state of bacterial cells. Increasing amounts of C-31 hydroxylated hopanoids with a temperature increase is novel information which deserves attention and further investigation for a better comprehension of the physiological significance of modifications conditioned obviously by environmental changes.

Thermomonas fusca sp. nov. and Thermomonas brevis sp. nov., two mesophilic species isolated from a denitrification reactor with poly(epsilon-caprolactone) plastic granules as fixed bed, and emended description of the genus Thermomonas.

Previously, 22 aerobic Gram-negative bacteria were isolated from biofilms growing on granules of the synthetic polyester poly(epsilon-caprolactone); the granules were used as a fixed bed in a denitrification reactor. All the strains showed similar fatty acid profiles. The 16S rRNA gene sequences of five strains were phylogenetically related to Thermomonas spp. Repetitive extragenic palindromic DNA-PCR (REP-PCR) fingerprinting revealed four groups, and DNA hybridizations between representative strains showed that the strains belonged to two new species within the genus Thermomonas, for which the names Thermomonas fusca (type strain LMG 21737(T)=DSM 15424(T)) and Thermomonas brevis (type strain LMG 21746(T)=DSM 15422(T)) are proposed. Both species are able to grow at low temperatures, but not at 50 degrees C, and are non-haemolytic. Both species can be differentiated by several other phenotypic features from earlier described species of the genus Thermomonas. Cell extracts contain mainly branched fatty acids, with C(15 : 0) iso, C(17 : 1) iso omega9c, C(11 : 0) iso 3OH and C(11 : 0) iso as main constituents. The G+C content of the DNA of the novel species is between 67.6 and 68.7 mol%.